You’ve brushed your teeth and you are headed to bed. Suddenly you remember something very important for tomorrow. You can’t forget. You can go write it down, send yourself an email, etc. but you really just want to go to bed. How can you make sure you remember?
Simple. Grab your shoe and put it on top of the toilet. In the morning, you’ll stumble into the bathroom, see the shoe and groggily think “What in the world is that doing there?” As your brain clears you’ll remember you put it there for a reason and soon you’ll be awake enough to recall what caused you to put the shoe there in the first place.
This is very similar to tying a string around your finger. You can do it with about anything. Just put something out of its ordinary place to help you remember.
If you are married, it might be a good idea to let your spouse in on what you are doing. Otherwise they might try to clean up after you and ruin everything–they may also begin to question your sanity if it happens too often.